256 



HYALONEMA (PRIONEMA) AGUJANUM. 



The stout- and shortr-rayed proximally smooth mon- to pentadine acanthophores 

 (Plate 76, figs. 8-16, 31, 32). The pentactine forms (Plate 76, fig. 32) are rare 

 and have been found only in var. tenuis, form A. They are very much smaller 

 than the others and may perhaps be spicules of another kind. The tetractine 

 forms (Plate 76, figs. 8, 10-13) with four fairly equally developed rays are 

 frequent in all the specimens. Their rays extend in the same plane and enclose 

 angles of 90°. They are usually straight and attenuated towards the end. 

 The triactine forms are not nearly so frequent. They are evidently tetractine- 

 derivates and differ from the true tetractines only by one ray being much reduced 

 or suppressed altogether. Transitions between the tetractines and triactines 

 (Plate 76, fig. 10) are by no means rare. The diactine forms (Plate 76, figs. 14- 

 16) are frequent. They sometimes possess, besides the two properly developed 

 rays, a rudiment of a third ray (Plate 76, fig. 15). Those without such a rudiment 

 are either centrotyle and spindle-shaped (Plate 72, fig. 14), or simply cylindrical 

 and rather thicker at the ends than in the middle (Plate 76, fig. 16). The mon- 

 actines (Plate 76, fig. 31) are rare. They appear as tylostyles. The dimensions 

 of these spicules are the following: — 



Hyalonema 

 (Prionema) 

 agujanum 



Only terminally spined, basal spicules with 



more or less fully developed rays 



CO t* 



3r^ 



4-^ t-i 



a s-s 

 •p. a §> 



V. a 



V. a 



." <D 



'i I o 



var. tenuis 



form A 



45 



167- 

 240 



14-17 



230- 

 295 



17-18 



117- 



320 



11-21 



194 



{oTmB 



140- 

 440 



11-28 



275- 

 340 



15-20 



570- 

 1400 



10-20 



190 



21 



17 



var. lata 



350- 

 530 



12-14 



870 



12 



all forms and 

 varieties 



14 



140- 

 530 



11-28 



230- 



870 



12-20 



117- 

 1400 



10-21 



190- 

 194 



17-21 



As the entirely spined short-rayed basal acanthophores are sufficiently 

 abundant for proper study and measurements only in the Palythoa, and as only 



